How Old is Old when considering an Amp? Krell, Bry

Personally I'd be wary of the Krell that old as the caps should probably be replaced. The Krell's run very hot. A newer one or a Classe, Bryston or Plinius are all good. You can get a Classe 201 for under 2k and a Bryston 4BST for around 1200. Both are good choices. The Plinius is an excellent choice too and whether or not you need the extra power I don't know. Of the three the Plinius may be the best amp but it can vary due to system synergy.

This is a very good question. I have some amps that are 40+ years old that work but required maintenance. On the other hand I am using a 30ish year old integrated in a second system that never needed any repairs and sounds great for what it is. I have found that an old ARC amp (solid state) from that period blows fuses once in a while and a Coda preamp from the same era- 1991 dropped a channel, I think I have a fat chance fixing that.
Krell I dare say is different. If you send them your amp they will refurb it for a price and you will have a sound that audio historians consider legendary. It might be worth buying with the full knowledge that your first move is sending it to Krell and you will have to invest a couple of hundred getting into excellent working condition, otherwise only buy old equipment you can afford to lose completely.

I can vouch for Classe's service. I have a CA-200 that had a little problem. I sent it to Classe where they fixed it, made some updates, and replaced the RCA jacks because they showed signs of normal wear. They didn't charge me anything but I did have to pay for shipping. I think I made out considering I'm not the original owner and the amp was out of warranty. Plus, it came back sounding more glorious than ever!

I'll never buy a component who's company offers little or no customer service. It's simply not worth it, especially if you're buying used.

i have a p300 accuphase that is 35 years old and has never been serviced. it performs flawlessly. it is possible for a quality ss amp to go for decades without service.

Krell is ok if you like bright harsh highs.